1. Field of the Disclosure
Embodiments disclosed herein relate generally to a process for the dimerization of isoolefins. More specifically, embodiments disclosed herein relate to processes for the selective dimerization of isoolefins using a metalized resin catalyst.
2. Background
Isobutene is commercially significant in many applications. For example, isobutene is one of the comonomers in butyl rubber. Isobutene can also be oligomerized to produce compounds that can be used as chemical feedstock for further reacting or in gasoline blending. Diisobutene, the isobutene dimer, is of particular commercial value in several applications. For example, diisobutene can be used as an alkylation reaction feedstock or as an intermediate in the preparation of detergents. Diisobutene can also be hydrogenated to pure isooctane (2,2,4 tri-methyl pentane) that is highly preferred in gasoline blending.
Isoolefin oligomerization is a catalytic reaction that uses an acid catalyst. For example, oligomerization of isoolefins has been disclosed in U.S. Pat. Nos. 4,242,530, 4,375,576, 5,003,124, and 7,145,049, 6,335,473, 6,774,275, 6,858,770, 6,936,742, 6,995,296, 7,250,542, 7,288,693, 7,319,180, 6,689,927, 6,376,731, 5,877,372, 4,331,824, 4,100,220 and U.S. Patent Application Publication Nos. 20080064911, 20080045763, 20070161843, 20060030741, 20040210093, and 20040006252, among others. Acid resin catalysts have also found use in various other petrochemical processes, including formation of ethers, hydration of olefins, esterifications, and expoxidations, such as described in U.S. Pat. Nos. 4,551,567 and 4,629,710.
When an isoolefin, in particular isobutene, is oligomerized, it is desired to limit the progress of the oligomerization reaction to the dimer stage. High dimer selectivity may be achieved by adding suitable moderator to the reaction mixture, for example, a certain polar component. Typically, oxygenates, such as water, primary, secondary and tertiary alcohols and ethers, are used as the moderator. Use of MTBE as a reaction moderator, for example, is disclosed in U.S. Pat. No. 4,375,576. U.S. Pat. No. 6,376,731 discloses use of tertiary butanol as a reaction moderator.
The presence of various water soluble or aqueous components used as reaction moderators, such as water, alcohols, and ethers, and operation of reactors at elevated temperatures may result in acid groups being removed from the catalyst (sometimes referred to as “acid throw”). The loss of acid from the solid catalyst may cause a low pH aqueous phase, often resulting in corrosion of reactor vessels and associated piping due to the acid.
Accordingly, there exists a continuing need for isoolefin dimerization catalysts and processes that may decrease or eliminate unwanted corrosion due to loss of acid from a catalyst.